The present invention relates to a liquid crystal display projector for magnifying and projecting images and, more particularly, relates to a structure for retaining the liquid crystal display panel and polarizing plate in place.
An LCD projector (hereinafter briefly called xe2x80x9cprojectorxe2x80x9d) which magnifies and projects an image on a liquid crystal display (LCD) panel by using such a light source as a metal halide lamp has so far been in practical use. The projector converges beams of light emitted from a light source on an LCD panel through mirrors and the like and projects an image displayed on the LCD panel onto a screen through a projecting lens.
FIG. 7 shows a color combining unit in a conventional projector. Each of LCD panels 50R, 50G, and 50B corresponding to red (R), green (G), and blue (B) color light components has a polarizing plate disposed on the exit light side. There is shown in FIG. 7 polarizing plate 51R on the exit light side of LCD panel 50R. These polarizing plates are cemented to three faces of dichroic prism 52 located in the center of the color combining unit through retaining members such as metal clamps 53R, 53B, and 53G, or fastened to the same with screws 54 or the like.
The color combining unit structured as described above is joined to optical base 55 produced by aluminum die casting or the like. Walls provided on optical base 55 secures projecting lens 56 in a position normal to prism 52. Fan 57 for cooling LCD panel 50, polarizing plate 51, and others and branch duct 58 for guiding air sent from fan 57 are joined to the lower portion of optical base 55.
FIG. 8 shows details of the color combining unit. FIG. 8A is a plan view and FIG. 8B is a front view. Exit-side polarizing plate 60G disposed on the exit light side of LCD panel 50G has a substrate made of glass or the like and a polarizing film pasted on one side of the substrate and the same is positioned between LCD panel 50G and dichroic prism 61. Polarizing plate 60G has air passages formed on both its faces. Air sent from fan 57 is passed through the air passages and, as a consequence of it, the air provides cooling for heated polarizing plate 60G. The same also applies to polarizing plates 60R and 60B.
It is desired that brighter and smaller projectors be provided. When a projector comes to have higher brightness, it is made possible for users to view a projected image on a large screen even in a light room. Therefore, such a projector has recently been put to practical use that, for example, uses a 1.3-inch LCD panel and provides a light output of 3000 ANSI lumens.
Further, a smaller projector takes less space for installation. In order to obtain higher brightness, it is required that the intensity of light from the light source be increased and, in order to reduce the size, it is required that components of the projector be made smaller. Hence, it is nowadays being practiced to produce small projectors by using, for example, a 0.9-inch or a 0.7-inch LCD panel.
On the other hand, the greater the intensity of light from a light source, and the smaller the size of the components of a projector, such as the LCD panel and polarizing plate, the light quantity thrown on a unit area of the polarizing plate increases. Consequently, the light quantity absorbed by the polarizing plate per unit area increases and the quantity of generated heat increases.
Further, use of a small LCD panel makes it difficult to firmly hold LCD panel 50 and polarizing plate 51 in place with metal clamps 53 and also makes it difficult to secure sufficient air passages.
It is an object of the present invention to provide a simple structure suppressing temperature rise occurring in a polarizing plate, especially that occurring in a polarizing plate on the exit light side, thereby reducing deterioration of the polarizing plate.
In an LCD panel of the present invention, a color separating unit separates beams of light from a light source into red, blue, and green color components. Each liquid crystal display (LCD) panel modulates each of separated red, blue, and green light components. An incident-side polarizing plate is disposed on the incident light side of the LCD panel and transmits polarized light in one direction. An exit-side polarizing plate is disposed on the exit light side of the LCD panel and transmits polarized light in another direction. A color combining unit combines modulated light beams. A projecting lens projects the combined light beams.
In a projector as described above, at least one of the incident-side polarizing plate and the exit-side polarizing plate is a polarizing plate unit having a first polarizing member provided on one face and a second polarizing member provided on the other face of a glass substrate.